1. Field of Invention
This invention relates to epoxide resin curing agents. More particularly, this invention pertains to novolac based polyamines which may be used to cure polyepoxides in aqueous based systems.
2. Prior Art
Solvent based epoxy resin curing agent systems have been known for many years. However, these solvent systems often are quite flammable, expensive and many have disagreeable odors.
Moreover, in recent years, increasingly strict regulation of environmental pollutants has lead to a limitation on the types and amounts of organic solvents which can be used in epoxy resin curable systems. The first approach to these limitations on the solvent content of coating systems was simply to employ a surfactant and emulsify or disperse existing polymeric systems in water. However, the cured products which resulted from these emulsions or dispersions often exhibited poor properties when compared to prior art solvent based systems. In particular, the chemical and water resistance of such systems was often lower because of the high levels of surfactant which were needed. Therefore, the search has continued to discover epoxy resin curing agent and curing agents systems which may be disbursed in water and which maintain the high performance levels of prior art solvent based systems.
U.S. Pat. No. 4,166,900 discloses cathodic electro deposition resin systems prepared based upon polyepoxides, polyamines and monoepoxides. While the monoepoxide and polyamine are similar to the products used in this invention, the polyepoxide utilized in U.S. Pat. No. 4,166,900 is quite different. Specifically in column 3, lines 47 to 68 there is no disclosure of the use of novolac type, highly branched, highly functional epoxy resins.
Likewise, U.S. Pat. No. 4,246,148 discloses an aqueous coating composition based upon an epoxy polyamine adduct end capped with monoepoxide. Again in the U.S. Pat. No. 4,246,148 it is made clear that highly functional, highly branched epoxides such as the novolac resin were not contemplated. Specifically in column 5, lines 10 to 20, a general formula is shown which clearly discloses a diepoxide, not a tri- or tetra-functional epoxide as contemplated by the applicant.
Thus it is the object of this invention is to prepare epoxy resin curing agents which are useful in aqueous based systems.
It is another object of this invention to prepare water based epoxy resin curing systems which exhibit properties which are equivalent to the properties of prior art solvent based systems.
These and other objectives are obtained by preparing the epoxide resin curing agents of the instant invention.